FEMA Flood Maps
The Federal Emergency Management Agency (FEMA) publishes a large set of “flood maps.” These paper maps are the official, Federally sanctioned source for determining flood risk. The flood maps delineate regions that are assigned a flood zone designation from among a limited set of possible designations.
For example, a region designated “Zone A” on a flood map is a high risk area, which FEMA believes has at least a 1 in 30 chance of flooding during any given year. A region designated “Zone V” combines the properties of a “Zone A” with the additional risk of wave action or flowing water. Other zone designations include “X,” “AE,” “B,” “C,” and “D,” see FIG. 2. In the foregoing context, performing a “flood zone determination” (also known as a “flood hazard determination” or a “flood certification”) relative to a location entails a two-step process: (1) determining, based on FEMA flood maps and other materials, the FEMA-designated flood zone for the location in question, and, then, (2) completing required paperwork to report this determination (along with certain other required information) to interested parties, such as home buyers, their lenders, and real estate brokers.
FEMA flood maps come in a variety of styles, but broadly speaking they can be divided into two types of maps, namely, index panels or index panel maps, see FIG. 5, and regular panels or regular panel maps, see FIGS. 1-4 and 7.
Referring to FIG. 1, a regular panel map 10 shows a relatively small geographic area at a fairly high level of detail. Each regular panel 10 depicts various “features” of the relevant area. These features include (without limitation) streets 12 railroad tracks 14, streambeds 16, lakes, intersections 18 of the foregoing, and detailed delineations of the boundaries of various extant flood zones 22(see FIG. 2) and their classifications.
FIG. 2 depicts a regular panel map 10 in which flood zones 22 are depicted. As is typical, the flood zones 22 are denoted or “flagged” as variously shaded regions contained within irregular curvilinear boundaries (the “flood zone boundary”). Legends or labels 30 on regular panels 10 designate the types of flood zones 22 that have been shaded. With the exception of regular panels 10 described as “not printed” (“PNP”) and panels presenting flood zone-designated communities, described in greater detail below, all flood zone determinations are made by reference to appropriate regular panel maps 10.
Continuing to refer to FIGS. 1 and 2, each regular panel map 10 is bounded by a “neatline,” that is, a rectangular frame or border 32 surrounding the geographic area 33 of interest. The geographic area of interest 33 may not completely “fill” the neatline 32, as indicated at 34 in FIGS. 1 and 2. For example, the actual geographic area 33 contained within the neatline 32 of a regular panel 10 might consist of (a) a portion 35 of a community and the designated flood classification of the portion and (b) unincorporated or other portions 36 which surround, are surrounded by, or abut the community, and which have no flood classification depicted on the panel 10.
Referring to FIG. 3, if FEMA has designated a regular panel map 10 as being applicable to determining the flood zone classification of only a portion 35 of an incorporated community, then the regular panel 10 cannot be used to determine the flood classification of any depicted unincorporated areas 38. According to FEMA protocol, the foregoing obtains whether or not flood zones for the unincorporated area are shown on the regular panel 10. Indeed, a FEMA panel map 10 often does not show flood zones for areas outside of the designated region for the map 10 (the designated region 35 is a portion of the community in this example). Sometimes the area outside of the designated area is just shown as a blank area on the panel, as at 38. Regardless of how much or how little detail is shown, by convention, a flood determination can be made using a panel 10 only in the region designated by FEMA.
The “inset” 44 of a panel 10 is any geographic region that is both shown on the panel 10 and as to which FEMA mandates the application of the flood zone designations set forth on the panel 10. A panel inset 44 may be self-connected (connected with all parts of itself) as in FIGS. 1-3, or, as shown in FIG. 4, it may comprise two or more self-connected regions 46,48 separated by one or more intervening, non-designated areas 50 on the panel 10 and may include other non-designated areas, such as those shown at 52 and 54. The insets 44 of a panel map 10 may comprise a collection of disjoint, self-connected regions 46,48 which collectively contain all of the designated area of the panel 10, and themselves constitute a subset of the geographic region contained within the neatlines 32.
Thus, from the foregoing, an actual map panel 10 consists, in general, of three parts: (1) the inset(s) 44, (2) other (non-designated) geographic regions 34,36,38,50,52,54 within the neatlines 32, which are not included within the inset(s) 44, and (3) areas of the panel which are outside of the neatlines 32, and generally show various types of textual information such as a map legend, the map panel number, and panel effective date, etc. It is true that, in the ideal case, an inset 44 should include only designated regions of the panel 10, but as a practical matter it is sometimes convenient to include some non-designated areas within the insets, so as to simplify the process of gathering inset border data.
Referring to FIG. 5, an index panel map 60 shows a considerably broader area than a regular panel 10, but at a lesser degree of detail, and usually without the flood zones being indicated thereon. Typically, an index panel 60 shows a broad geographic view of the locations of the various regular panels 10 that make up an entire community, or other large geographic area. It should be noted that, while FEMA “defines” communities, these FEMA-defined communities often do not correspond to one's intuitive sense of what a community is.
The index panel 60, generally depicted in FIG. 5, provides its broader, less detailed overview by displaying an “outline” of regular panels 10, that is, the neatline boundaries 32 of each of its regular panels 10 against a background of major geographic features (e.g. municipal boundaries, highways, lakes, etc.). The outlines of the regular panels 10 bear legends or labels informing of the corresponding designation of its regular map panel 10, as represented by “XX,” “YY” and “ZZ” in FIG. 4. The designations “XX,” etc. are set forth on the panels 10 outside the neatlines 32. Index maps 60, in effect, show how to “put together” the panel map 10 “jigsaw”, that is, how to associate panel maps 10 with each other to form a grid thereof, grid lines 62 thereof being comprised of the aligned and/or overlapping neatlines 32 of adjacent panels 10.
Until the advent of the present invention, the primary purpose of the index maps 60 has been their use as an aid in manually determining which of the panel maps 10 should be consulted in order to make a flood zone determination. For example, if a property is known to be located in Community A, then a map analyst might first locate the property on the Community A index map 60. The analyst could immediately determine - - - by examining the neatline borders 32,62 and the labels “XX,” “YY,” “ZZ” displayed on the index map 60 - - - which regular panel map 10 to consult. Since there are hundreds of panel maps 10 in the index map 60 of various communities, identification of a particular panel map 10 by examining an index map 60 can be effected more quickly than serially examining large numbers of panel maps 10. The present invention provides other, much more efficient ways of determining the correct regular panel map 10 applicable to a particular location.
Index maps 60 also contain neatline borders 32 for panel maps 10 that are not printed as such, and which are designated “panel not printed” or “PNP.” As this name suggests, no actual panel map 10 is ever printed for a PNP. Instead, the relevant index map 60 displays the flood zone classification for the region contained within the PNP neatline borders 32. Accordingly, In the case of a PNP, the flood zone classification is determined from the index map 60, rather than from a regular panel 10.
In addition to the foregoing techniques, flood zone determinations can also be made on the basis of FEMA's denoting certain communities as “flood zone designated communities.” In this event, FEMA mandates that a denoted community have the same flood zone classification throughout. As a consequence FEMA does not publish any flood panels - - - either regular 10 or index 60 - - - for the community. A property located anywhere in that community assumes the flood zone classification of the community.
Digital Raster Maps
A digital raster map image may be thought of as a number of points selectively present at each X,Y coordinate of a Cartesian display. These points are usually called “pixels.” Besides having an address at an X,Y location, a pixel may have a “value,” usually a numeric quantity designating a specified color or grey-scale value for the pixel. The X,Y location and value of each pixel is data that may be stored. A digital raster map may be created by optically, digitally scanning a conventional paper map and thereafter using a computer system to define and/or display it in terms of its pixel locations and color values. Commonly used formats for storing scanned images currently include TIFF, JPEG, and PNG. Any FEMA regular panel 10 or index panel 60 may be represented as a digital raster map.
Digital Vector Maps
A vector map may be viewed as a “virtual” map that comprises, in effect, a collection of stored data. The stored data define the locations of plural nodes and plural straight-line segments interconnecting the nodes. The stored data defining a vector map represents geographic information in the form of collections of points - - - the nodes - - - and line segments interconnecting the nodes to form polygons, i.e., closed figures comprised of line-interconnected nodes. These points, lines, and polygons may have additional information associated with them. For example, the stored data may indicate that a particular point or node is the location of the capitol building, or that a selected polygon describes the border of Lake Placid. The polygons are surrogates for, or representations of, the actual curvilinear configuration of various geographic features: streets, streams, lakes, cities, counties, etc. Typically, the features - - - nodes alone or two or more interconnected nodes - - - are presented in terms of latitude/longitude (or lat/lon) values. If this or another earth-referenced system is used to locate the nodes of the map, the map is said to be georeferenced. A visually sensible map may be “drawn” from the stored data.
In view of the fact that georeferencing of digital raster map images plays a key role in the present invention, the precise meaning of this term, for the purposes hereof and as used herein, is set forth below.
Georeferencing
A raster map image is said to be “georeferenced” if there exist mathematical functions, f and g, such that one function can be used to convert the X,Y coordinates of the pixels describing the map image to corresponding latitude/longitude coordinates and the other function can be used to convert the latitude/longitude coordinates of the pixels of the image to their corresponding X,Y coordinates. In other words, f and g effect the following:
1. If (x, y) represents a pixel location on a digital raster map image, then f(x, y)=(Lon, Lat) represents the longitude and latitude of the corresponding physical location; and
2. If (Lon, Lat) represents a physical location that lies within the region covered by the map, then g(Lon, Lat)=(x, y) represents the point on the digital raster map image that corresponds to that longitude and latitude.
In the previous paragraph, (x,y) defines a point pursuant to the natural internal coordinate system of the raster map image. Most digital vector map images use longitude and latitude as their internal coordinate system. Accordingly, most digital vector maps can be considered to be trivially georeferenced per se. Most digital raster map images use the pixels of its image as a kind of natural coordinate matrix. Such a raster map image is not inherently trivially georeferenced and requires the operation of a non-trivial georeferencing function to convert back and forth between coordinate systems.
Most FEMA maps do not contain any latitude/longitude information that would be useful in georeferencing their scanned raster image. Some recently FEMA-issued panels do show latitude/longitude values at certain points thereon, but such panels are in a distinct minority when considered in the context of the 100,000+ panels that FEMA currently provides.
Before real property is bought, sold, or insured, it is common practice to examine the property for the risk of flooding. This is commonly done by examining a map depicting the flood zone in which the property is located. The Federal Emergency Management Agency (FEMA) assigns flood zone classifications and publishes a library of ten of thousands of paper maps showing the various flood zones and their locations in the United States. A determination of whether a property resides in a flood zone and, if so, the classification of such flood zone has, until the advent of the present invention, been typically performed in the following manner.
First, the address of a selected parcel of real property is examined, and the location of the property is determined as a consequence thereof. This may be achieved, for example, through the use of a geocoding system, or by examining an available street map. Next, a map analyst attempts to determine which one(s) of the many thousands of FEMA flood maps contain or depict the location of the property. This determination may entail false starts, dead ends and misdirection and may occasionally require hours of effort before the identity of the flood map containing the property is found. During this process the map analyst may retrieve, from map storage, and view numerous paper maps before determining the one containing the property's location.
Third, having retrieved the required paper map, the map analyst next determines where the property is located on the FEMA map. Finally, the map analyst examines flood zone notations on the map at the property's location in order to determine its flood zone status.
This foregoing manual process can be somewhat improved by scanning the paper FEMA maps into a computer to produce stored digital raster maps, which can be retrieved and viewed as necessary. A digital raster map is a map image that resembles a conventional paper map in that it presents an image of the mapped area, but has no additional underlying data associated with the features of the map. A raster map is typically created by scanning a conventional paper map, and is a grid-based map composed of pixels (or dots) of color or black and white. Each pixel in the grid can be referenced by Cartesian X,Y pixel coordinates, and has an associated value indicating the color of the pixel. Raster images are commonly referred to as “bit mapped” images.
A vector map comprises polygons - - - nodes connected together with straight line segments - - - rather than pixels, to describe an image. Unlike a raster map, in which the map image is simply stored and displayed as a grid of pixels each having an X,Y coordinate, a vector map is drawn from a set of underlying data stored, for example, in a computer memory. A vector map is created through the placement of the nodes on a plane and the connection together of those nodes with straight-line segments. The nodes and lines may be attributed with stored tables of data such as elevations, values, names or other information relative. Vector data can be displayed in three dimensions if the lines are attributed with z values, modified or changed relative to user need, or layered to allow for turning off and on the viewing of different information.
Because of their feature attribution properties, vector maps are particularly useful for displaying geographic data on a computer system. Vector maps are used to display boundaries or lines that denote the position and extent of features, such as county boundaries or lines denoting stream and river systems. It is also very easy to view or manipulate the data underlying a vector map, for example to view or change the elevation of a feature.
Also, because vector maps are drawn from stored data which describe the locations of features shown, they are often inherently georeferenced. Georeferencing is the process of relating source coordinates to referenced geographic coordinates, which are typically in standard latitude/longitude. An image or a vector file is georeferenced to be used within a mapping/geographic environment. In a vector map, the data from which the map is drawn will typically already include a geographic coordinate set.
Modern GIS systems normally make use of digital vector based map information. However, a vast legacy of paper based map information exists. It is very expensive and time consuming to convert all of the information on these paper maps to a digital vector format. In many cases the scope and expense of such conversions render them completely impractical. However, even when a complete conversion to digital vector-based format is not feasible, it is still possible to obtain some of the benefits of computerized map systems by converting the paper maps to digital raster maps (by scanning them), followed by georeferencing the raster images. After georeferencing, there is a clear relationship between the X,Y coordinates of each pixel in the raster map, and the geographic - - - latitude, longitude - - - coordinates of each pixel.
Since flood zone determinations are typically performed using paper FEMA maps, it would be desirable to provide a system and method for performing flood zone certifications that is faster and can be performed less expensively than the process described above.